Dual-roller crushers are known and common particularly in the field of comminution in mining. In conventional dual-roller crushers, the size reduction of coarse rock or the like is done by two motor-driven rollers. As a rule, the rollers are horizontally aligned, with their central axes parallel to each other. The two rollers rotate in opposite directions of rotation such that the material to be crushed, which as a rule is supplied from above to the nip, is drawn into the nip by the rotation of the rollers and crushed by the crusher teeth. The material is then discharged downward from the nip. It is typical for crusher teeth to be mounted on the roller faces for the reduction in size of the supplied material to occur. The crusher teeth are provided with differing arrangements from one another on the roller faces. They are preferably arranged such that the teeth of one roller do not collide with the crusher teeth of the other roller during rotation of the rollers.
A synchronization of the rollers by a gear is also known.
In classic dual-roller crushers there exists an imaginary tangential opening angle between the two roller surfaces where the feed material is wedged and crushed between the rollers. A roller surface without teeth draws in the material for wedging of the feed material. In this case, only rock which is small in comparison to the size of the diameter of the rollers can be comminuted. The working tangential opening angle here is very small. The use of crusher teeth can significantly improve catchment depending on the geometry. Crusher teeth can have a wide variety of shapes, for example, they may be pointed teeth or chisel-like or fin-like crusher teeth that are fixed in a holder on the roller surface, preferably interchangeably, and such crusher teeth may have, for example, hardened tips and preferably project approximately tangentially to the outer surface. In conventional dual-roller crushers, the grain size achieved by reduction in size of the supplied materials by the dual-roller crusher is determined by the nip. The nip is in turn dependent on the tooth size. A large nip with correspondingly large teeth on the roller surface means that the final grain size after leaving the dual-roller crusher is relatively large. This means that in practice, a pre-crushing dual-roller crusher with relatively large teeth is used. Thereafter, however, post-crushing with a second dual-roller crusher is necessary, the second dual-roller crusher having smaller teeth so that its nip is smaller.